Technical discussion: lower compression on front rotor vs. rear rotor
#1
Technical discussion: lower compression on front rotor vs. rear rotor
Results from the 10 compression tests done last weekend at the meet point to the fact that in all cases, the front rotor had lower compression values than the rear.
This certainly cannot be explained coincidence or whether the engine was built on a Monday or a Friday.
So why do you guys think this is happening? Let's discuss...
This certainly cannot be explained coincidence or whether the engine was built on a Monday or a Friday.
So why do you guys think this is happening? Let's discuss...
#2
My front rotor actually scored higher than my rear, however this is the cars second engine. Not sure what to make of that if anything.
Last edited by livelycorpse; 05-02-2012 at 01:34 PM. Reason: iPhone auto correct.
#4
no agenda
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Footman we should try to get everyone to post their compression tests.
Now I've been thinking about this topic as I knew you had a bit of a thing for it.
I was trying to think if there was something that could induce this common ... result
All I can think of is that I always did the front rotor first as so that would make it a few degrees warmer then the rear when tested.
However it would also mean the rear had an cycle of "deflood" before getting tested
That all being said speaking with FazdaRX8 he recalls most engine failures to be on the front. There was another member present at the meet as well that says both his engines failed on the front.
I do think there is something to this but the analitical boyz will want their fill
Now I've been thinking about this topic as I knew you had a bit of a thing for it.
I was trying to think if there was something that could induce this common ... result
All I can think of is that I always did the front rotor first as so that would make it a few degrees warmer then the rear when tested.
However it would also mean the rear had an cycle of "deflood" before getting tested
That all being said speaking with FazdaRX8 he recalls most engine failures to be on the front. There was another member present at the meet as well that says both his engines failed on the front.
I do think there is something to this but the analitical boyz will want their fill
#6
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IIRC the coolant from the radiator enters the rotor housing via the rear rotor on the cold side (driver side), exits out the front on the cold side and enters the hot side of the housing on the front of the motor (passenger side) and exits at the back of the hot side.
Consider hot exhaust gases travel away from the front...
I'm not sure about lubrication.
Consider hot exhaust gases travel away from the front...
I'm not sure about lubrication.
#9
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The fall outs on older series FC/FDs have lower compression in the rear rotor. It would be interesting to see and note the revisions made and maybe gather some correlation in between.
#10
My results may be contrary to your hypothesis however I did find it odd that my front rotor results were all around 4 or 5 psi higher (3 or 4 when calculated to 250 rpm). Is this coincidence? Or perhaps something contrary was done during my test not done during others tests? I have no idea as I have a very VERY basic understanding of all this, just trying to examine with a critical eye.
Front 113 117 112 - 115.8 119.9 114.7
Rear 109 112 107 - 112.9 115.9 110.8
Front 113 117 112 - 115.8 119.9 114.7
Rear 109 112 107 - 112.9 115.9 110.8
#11
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#14
Hate Scrape 8
this was done back when I was having misfiring issues with my car and found I had the incorrect ECU in my car. Had a Cali Spec ECU (Which I have laying around, WCS you have any use for it?)
![](http://i46.tinypic.com/21537o.jpg)
#15
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welp.. compression was waaaayyyy lower in my second rotor then my first..... didn't matter though since the engine failed on all faces (spectacularly I might add).
I'm now going through the new break in period on the new engine/clutch.... can't wait or it to be over.
I'm now going through the new break in period on the new engine/clutch.... can't wait or it to be over.
#23
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Danka. It's hard having to roll around under 4k. I had a new clutch installed as well seeing as how the springs were pretty much dead in the OEM.
![Wink](https://www.rx8club.com/images/smilies/wink.gif)
#24
Yes, new clutch and new flywheel too. Since I still have manufacturer's warranty left on this engine, I didn't want to chance with a RB flywheel. Though once the warranty is out, that's what I'll be doing. The flywheel comes with the engine block.
I drove almost 2 months below 4000 rpm... it's tough!
I drove almost 2 months below 4000 rpm... it's tough!
#25
Sorry for posting my results so late. But believe it or not this is the first time I noticed this post.
Front Rotor 114 119 121 Corr. Factor 118.5 123.6 125.7
Rear Rotor 118 118 122 Corr. Factor 122.6 122.6 126.8
Normalized to 250 rpm
Front Rotor 111.3 116.4 118.5
Rear Rotor 114.0 114.0 118.3
Front Rotor 114 119 121 Corr. Factor 118.5 123.6 125.7
Rear Rotor 118 118 122 Corr. Factor 122.6 122.6 126.8
Normalized to 250 rpm
Front Rotor 111.3 116.4 118.5
Rear Rotor 114.0 114.0 118.3
Last edited by SSilver07-RX8; 05-30-2012 at 05:56 PM. Reason: Added Normalized to 250 rpm